In the last 20 years, computers have played an ever increasing role in the airline industry. For example, computers are used onboard an aircraft for such tasks as aiding navigation, scheduling maintenance, monitoring the operation of equipment as well as for controlling the position of the flight control surfaces to fly the aircraft. On the ground, computers are used to ticket passengers, keep track of luggage, maintain records of seat availability, schedule departure changes, etc. In the past, there has only been a limited exchange of data between the aircraft computer system and the ground-based computer system used by an airline. Such exchange usually took place by hand carrying a floppy disk between the two computer systems.
Since the invention of computer networks, there has been considerable effort within the airline industry devoted to developing a communication system that connects the aircraft computer system to the ground-based computer system. Early efforts used digital radio but were unsuccessful because of the limited bandwidth available due to radio frequency spectrum allocation and contention/interference. One suggested method of establishing a higher bandwidth communication system was to connect the two computer systems together using a fiber optic communications link. In such a system, a fiber optic cable would extend from the ground-based computer system to a fiber optic cable connector disposed on the side of the aircraft. As the aircraft taxied into a dock, a member of the maintenance crew could plug the fiber optic cable into the side of the aircraft, thereby allowing the data communication to take place. However, such a solution was deemed undesirable due to the fragile nature of fiber optic cable connectors and the need for ground crew action. Additionally, it is possible that the aircraft could pull away from the dock without disconnecting the cable, causing subsequent delays and extensive damage to the fiber optic cable and aircraft.
To overcome the problems associated with a fiber optic cable-based communication system, an alternate communications scheme was suggested by the airlines industry. The alternate scheme involved the use of a free-space optical communications system that could transmit information between the aircraft computer system and the ground-based computer system using a modulated infrared light beam. The free-space optical communications system would eliminate the need for the fiber optic cable possible damage from the aircraft pulling away and disconnecting the cable. However, current free-space optical communications systems suffer from at least three problems that, in combination, prevent such communications systems from being readily usable in an aircraft to ground-based computer communication link. First, current free-space optical communications systems do not operate at the high data rate that the airlines are requiring for a commercially viable communication system. For example, the Aeronautical Radio Incorporated (ARINC) standards group is currently developing a communications protocol that requires data communication between an aircraft and a ground-based computer system be accomplished at speeds of 100 Mbits/sec. Second, current state of the art high-speed, free-space optical communications systems often have a narrow field of view and, as such, require additional control systems to align the optical transceivers to ensure proper data transmission. Including such control systems into a free-space optical communications system adds significantly to the cost of the system, as well as introduces a likely source of system failure. Finally, current free-space optical communications systems will not operate in all types of weather conditions experienced at an airport.
Therefore, a need exists for a free-space optical communications system that can transmit data between an aircraft and a ground-based system at high speeds over all weather conditions. Additionally, the communication system should have a wide field of view to eliminate the need for any control systems to align the optical components of the system.